Semipermeable membrane support

Abstract

Disclosed is a semipermeable membrane support and a process for making the same. The support is formed of a non-woven fabric of a laminated structure having a low density layer with an air permeability of 5 to 50 cc/cm 2 /sec and a high density layer with an air permeability of 0.1 cc/cm 2 to 5 cc/cm 2 /sec, the non-woven fabric having an overall air permeability of 01 to 4.5 cc/cm 2 /sec. The process for preparing such a support consists of laminating a dry processed web, which is entirely of polyester fibers containing 20 to 80% of undrawn polyester fiber or conjugate polyester fibers having an average fiber denier of 1 to 3 denier formed through a dry process, and an un-press-treated wet processed web, which is entirely of polyester fibers containing 30 to 90% of undrawn polyester fibers or conjugate polyester fibers having a fiber denier of 0.1 to 1.5 denier formed through a paper making process and subsequent drying process with hot air to self-bond lightly, pressing the laminated dry processed web and wet processed web with a heated calendar at a sufficient temperature for bonding firmly the laminated webs.

What is claimed is: 
     
       1. A semipermeable membrane support comprising a non-woven fabric of a laminated structure having a low density layer with an air permeability of 5 to 50 cc/cm 2  /sec and a high density layer with an air permeability of 0.1 cc/cm 2  /sec to 5 cc/cm 2  /sec, said non-woven fabric having an overall air permeability of 0.1 to 4.5 cc/cm 2  /sec. 
     
     
       2. The semipermeable membrane support of claim 1, wherein the non-woven fabric comprises entirely polyester fibers containing 30 to 80% of undrawn polyester fibers or conjugate polyester fibers. 
     
     
       3. The semipermeable membrane support of claim 1, wherein the weight ratio of the low density layer to high density layer is in a range from 7:3 to 2:8, and the overall weight of the non-woven fabric is in a range of 70 to 250 g/m 2 . 
     
     
       4. The semipermeable membrane support of claim 1, wherein the fabric is used for preparing a semipermeable membrane through casting of a polymer solution for forming semipermeable membrane to form a membrane. 
     
     
       5. A semipermeable membrane having a support, said support comprising a non-woven fabric of a laminated structure having a low density layer with an air permeability of 5 to 50 cc/cm 2  /sec and a high density layer with an air permeability of 0.1 cc/cm 2  /sec to 5 cc/cm 2  /sec, said non-woven fabric having an overall air permeability of 01 to 4.5 cc/cm 2  /sec. 
     
     
       6. The semipermeable membrane of claim 5, wherein the non-woven fabric comprises entirely polyester fibers containing 30 to 80% of undrawn polyester fibers or conjugate polyester fibers. 
     
     
       7. The semipermeable membrane of claim 5, wherein the weight ratio of the low density layer to high density layer is in a range from 7:3 to 2:8, and the overall weight of the non-woven fabric is in a range of 70 to 250 g/m 2 . 
     
     
       8. The semipermeable membrane of claim 5, wherein the membrane is formed on the support by casting a polymer solution thereon. 
     
     
       9. The semipermeable membrane of claim 5, wherein the support is formed from a dry processed web, which comprises entirely polyester fibers containing 20 to 80% of undrawn polyester fiber or conjugate polyester fibers having an average fiber denier of 1 to 3 denier formed through a dry process, and an un-press-treated wet processed web, which comprises entirely polyester fibers containing 30 to 90% of undrawn polyester fibers or conjugate polyester fibers having a fiber denier of 0.1 to 1.5 denier formed through a paper making process and subsequent drying process with hot air to self-bond lightly, pressing said laminated dry processed web and wet processed web with a heated calender at a sufficient temperature for bonding firmly the laminated webs. 
     
     
       10. The semipermeable membrane of claim 9, wherein the wet processed web contains 20 to 70% of fibers with modified cross-section such as elliptic or Y-shaped cross-section. 
     
     
       11. The semipermeable membrane of claim 10, wherein the wet processed web is formed through a paper making process and is subsequently exposed to a drying process with hot air to self-bond lightly. 
     
     
       12. The semipermeable membrane of claim 9, wherein the dry process is a carding process. 
     
     
       13. The semipermeable membrane of claim 9, wherein the support is for preparation of semipermeable membrane through casting a polymer solution for semipermeable membrane to form a membrane.